She was dubbed "the world's greatest athlete" after taking decathlon gold at the 1976 Olympics and becoming an overnight American hero.
But the former Bruce Jenner - now Caitlyn Jenner after becoming a transgender woman - says she works harder at her make-up than she ever did at winning gold.
Writing in her new autobiography, serialised in You magazine, Jenner reveals: "Applying make-up is always intense and I sometimes think I work harder on it than I did to win the decathlon.
"I secretly bought how-to books since there was nobody to help me."
She also reveals how she stole clothes and make-up from her wife Kris, and her daughters and stepdaughters, including Kim Kardashian, whom she has starred with in the hit American reality TV series Keeping Up With The Kardashians.
Jenner, 67, writes movingly about her years of cross-dressing when she was still hiding the secret of her gender identity from the world, and the agonies her secret existence entailed. Recalling a speech in Orlando, Florida, while still known as Bruce Jenner, she writes of her audience: "They know what they want to hear: a life defined by those two days at the Olympic stadium when I broke the world record and ran around the track waving a small American flag.
"They don't know that underneath the dark blue business suit, I am wearing panties, a bra and tights."
The one-time college American football player adds: "They don't know that when I look in the mirror, I see something entirely different, a body that I fundamentally loathe."